Response of epithelial cells infected by Treponema denticola.

OBJECTIVE: In the gingival crevice, the interaction between epithelial cells and periodontopathic bacteria is important for the development of periodontitis. Treponema denticola is a major pathogen of chronic periodontitis and possesses several virulence factors, such as major surface protein (Msp) and prolyl-phenylalanine-specific protease (dentilisin). Here, we investigated the behaviours of epithelial cells infected with T. denticola by measuring the expression of interleukin (IL)-1ß, IL-6, ß defensin 2 (BD-2) and heat-shock protein 70 (HSP70). METHODS: Epithelial cells were infected with T. denticola wild-type strain, Msp-deficient mutant or dentilisin-deficient mutant, and the expression levels of the above targets were analysed by polymerase chain reaction. RESULTS: Infection with T. denticola wild-type strain and mutants induced the production of IL-6 and HSP70. The level of BD-2 induced by T. denticola wild-type strain at 24 hr was significantly higher than that of the dentilisin-deficient mutant. The level of IL-1ß mRNA in the wild-type strain and dentilisin-deficient mutant was slightly lower than that in the uninfected control. CONCLUSION: These results suggest that the levels of BD-2 were affected by Msp and dentilisin. This effect may contribute to the disruption of the response of epithelial cells to eradicate T. denticola.

Role of mitogen-activated protein kinase pathways in migration of gingival epithelial cells in response to stimulation by cigarette smoke condensate and infection by Porphyromonas gingivalis.

BACKGROUND AND OBJECTIVE: Previous studies have shown that cigarette smoke (CS) and periodontal pathogens could alter wound healing responses of gingival epithelial cells. To elucidate molecular mechanisms leading to these epithelial changes, we studied the signaling pathway involved in the modulation of cell migration by CS condensate (CSC) and the infection by a prominent periodontal pathogen, Porphyromonas gingivalis. MATERIAL AND METHODS: Human gingival epithelial cells (Ca9-22) were treated with CSC or vehicle control for 24 h. Activation of mitogen-activated protein kinases (MAPK) in cells with or without infection by P. gingivalis was assessed by polymerase chain reaction array and immunoblotting using phospho-specific antibodies. Cell migration was assessed using in vitro wound closure model, and specific pharmacologic inhibitors of MAPK pathways were used to characterize further the extent of involvement of the MAPK pathways. RESULTS: Polymerase chain reaction array showed that gene expression of several members of the MAPK, particularly p38 and JNK, was upregulated more than twofold in Ca9-22 cells stimulated with 10 µg/mL CSC. Coincubation with P. gingivalis induced a different pattern of gene expression for MAPK pathways, but it did not suppress the MAPK-related genes upregulated by CSC. A significant phosphorylation of ERK1/2 and p38 was observed in cells stimulated with 10 µg/mL CSC (p < 0.05), whereas coincubation with a higher concentration of CSC (250 µg/mL) evoked no such activation. P. gingivalis infection resulted in a tendency to reduce the phosphorylation of ERK1/2 and p38, which had been enhanced by stimulation with 10 µg/mL CSC. Incubation with ERK1/2 and p38 inhibitors significantly reduced the wound closure of CSC-stimulated cells, by approximately 43% and 46%, respectively (p < 0.05). CONCLUSION: CSC exerts effects on the migration of human gingival epithelial cells through the activation of the MAPK ERK1/2 and p38 signaling pathways. P. gingivalis infection attenuates the CSC-induced migration at least partly by suppressing the phosphorylation of ERK1/2 and p38, but other pathways are likely to be involved in this modulatory process.

Cigarette smoke condensate modulates migration of human gingival epithelial cells and their interactions with Porphyromonas gingivalis.

BACKGROUND AND OBJECTIVE: Epithelial cells are recognized as the first line of defense against bacterial infection and environmental harmful stimuli such as cigarette smoke (CS). Although previous studies explored the effects of nicotine on host cells, mechanisms by which CS affects cellular functions remain uncertain. The present study investigated the effects of CS condensate (CSC) on in vitro wound closure of gingival epithelial cells and their potential interactions with a major periodontal pathogen, Porphyromonas gingivalis. MATERIAL AND METHODS: Human gingival epithelial cells (Ca9-22) were treated with CSC for 24 h. Cell proliferation was determined using a WST-1 assay. Cell migration was assessed using a wound closure model. The expression of integrins was analyzed by confocal scanning laser microscopy and real-time PCR. Intracellular invasion of P. gingivalis was evaluated by confocal scanning laser microscopy and an antibiotic protection assay. RESULTS: Low concentrations (1-10 µg/mL) of CSC showed no significant effect on cell proliferation. CSC demonstrated dual effects on epithelial wound closure of Ca9-22 cells: high concentrations (i.e. 250 µg/mL) significantly inhibited the wound closure whereas low concentrations (i.e. 10 µg/mL) promoted it (p < 0.01). CSC induced distinct changes in cytoskeleton. When CSC-exposed cells were infected with P. gingivalis for 2 h, a significant inhibition of wound closure was observed concurrent with a decrease in integrin α3 expression near the wound area. A significantly increased P. gingivalis invasion into Ca9-22 was observed when exposed to low concentrations of CSC. CONCLUSION: Low concentrations of CSC increased invasion of human gingival epithelial cells by P. gingivalis and induced changes in cytoskeleton and integrin expression, thereby modulating the cell migration.

Pathogenicity of exopolysaccharide-producing Actinomyces oris isolated from an apical abscess lesion.

AIM: To demonstrate a capacity for producing exopolysaccharides (EPSs) and an ability to form biofilm on abiotic materials of Actinomyces oris strain K20. METHODOLOGY: The productivity of EPSs and the ability to form biofilm of strain K20 were evaluated by measuring viscosity of spent culture media and by scanning electron microscopy (SEM) and the biofilm assay on microtitre plates, respectively. High-performance liquid chromatography was used to determine the chemical composition of the viscous materials. To examine the role of the viscous materials attributable to the pathogenicity in this organism, the ability of strain K20 to induce abscess formation was compared in mice to that of ATCC 27044. RESULTS: The viscosity of the spent culture media of K20 was significantly higher than that of ATCC 27044. Strain K20 showed dense meshwork structures around the cells and formed biofilms on microtitre plates, whereas ATCC 27044 did not. Chemical analysis of the viscous materials revealed that they were mainly composed of neutral sugars with mannose constituting 77.5% of the polysaccharides. Strain K20 induced persistent abscesses in mice lasting at least 5 days at a concentration of 10(8) cells mL(-1), whereas abscesses induced by ATCC 27044 healed and disappeared or decreased in size at day 5. CONCLUSIONS: Strain K20 produced EPSs, mainly consisting of mannose, and formed biofilms. This phenotype might play an important role for A. oris to express virulence through the progression of apical periodontitis.

Surface grafting of biocompatible phospholipid polymer MPC provides wear resistance of tibial polyethylene insert in artificial knee joints.

OBJECTIVE: Aseptic loosening of artificial knee joints induced by wear particles from a tibial polyethylene (PE) insert is a serious problem limiting their longevity. This study investigated the effects of grafting with our original biocompatible phospholipid polymer 2-methacryloyloxyethyl phosphorylcholine (MPC) on the insert surface. METHODS: The hydrophilicity of the PE surface was determined by the contact angle of a water droplet, and the friction torque was measured against a cobalt-chromium alloy component. The wear amount was compared among PE inserts with or without cross-linking and MPC grafting during 5x10(6) cycles of loading in a knee joint simulator. The surfaces of the insert and the wear particles in the lubricant were subjected to electron and laser microscopic analyses. The mechanical properties of the inserts were evaluated by the small punch test. RESULTS: The MPC grafting increased hydrophilicity and decreased friction torque. In the simulator experiment, the wear of the tibial insert was significantly suppressed in the cross-linked PE (CLPE) insert, and even more dramatically decreased in the MPC-grafted CLPE insert, as compared to that in the non-cross-linked PE insert. Surface analyses confirmed the wear resistance by the cross-linking, and further by the MPC grafting. The particle size distribution was not affected by cross-linking or MPC grafting. The mechanical properties of the insert material remained unchanged during the loading regardless of the cross-linking or grafting. CONCLUSION: Surface grafting with MPC polymer furnished the PE insert with wear resistance in an artificial knee joint through increased hydrophilicity and decreased friction torque.

Analysis of matrix metalloproteinase (MMP-8 and MMP-2) activity in gingival crevicular fluid from children with Down's syndrome.

BACKGROUND AND OBJECTIVE: High levels of colonization by periodontopathic bacteria and a high prevalence of chronic inflammatory periodontal disease have been reported in children with Down's syndrome. Matrix metalloproteinases (MMPs) are mediators of extracellular matrix degradation and remodelling, and are deeply involved in the course of periodontal disease. To clarify the relationship between Down's syndrome and periodontitis, we investigated levels of MMP-2 and MMP-8 in gingival crevicular fluid (GCF) and detection of periodontopathic bacteria from subgingival plaque. MATERIAL AND METHODS: Samples of GCF and plaque were isolated from central incisors. Levels of MMPs were evaluated by enzyme-linked immunosorbent assay, and periodontopathic bacteria were detected by polymerase chain reaction. RESULTS: Levels of MMP-2 and MMP-8 in Down's syndrome patients were higher than those in healthy control subjects. In the Down's syndrome group, increases in these MMPs were observed in GCF from patients with an oral hygiene index score of < 2 and in GCF from sites that were negative for bleeding on probing. The detection rate of periodontopathic bacteria in Down's syndrome patients was higher than that in the control subjects. Matrix metalloproteinase-2 levels in sites harbouring Porphyromonas gingivalis or Aggregatibacter (Actinobacillus) actinomycetemcomitans were lower than in those without these microorganisms. CONCLUSION: These results suggest an increase in MMP-2 and MMP-8 in Down's syndrome patients, regardless of whether inflammation of periodontal tissue is present or not.

Oral environmental factors affecting number of microbes in saliva of complete denture wearers.

The purpose of this study was to clarify which oral environmental factors affected number of microbes in saliva in an edentulous environment. We enrolled 68 edentulous subjects in the study. Numbers of total anaerobic bacteria and Candida species in saliva were determined. Age, sex, un-stimulated salivary flow rate, pH and viscosity of saliva, histatin level in saliva, tongue coating status, tongue pressure, denture plaque status, material of denture base, duration of edentulism, frequency of self oral health care and number of cigarettes per day were also investigated as oral environmental factors. Correlation between number of total anaerobic bacteria or Candida species and each oral environmental factor was determined with the Spearman rank correlation coefficient. Stepwise logistic regression analysis was used to identify which factors were significantly associated with level of total anaerobic bacteria and Candida species. Correlation and stepwise logistic regression analyses revealed associations between un-stimulated salivary flow rate, tongue coating status, denture plaque status or frequency of self oral health care and number of total anaerobic bacteria. The correlation analysis showed a significant correlation between age and number of total anaerobic bacteria. Stepwise logistic analysis revealed associations between pH of saliva or viscosity of saliva and level of anaerobic bacteria; it also revealed associations between histatin level in saliva or un-stimulated salivary flow rate and level of Candida species. We conclude that salivary flow rate, in particular, affects number of salivary microbes in an edentulous environment.

Characterization of bacterial flora in persistent apical periodontitis lesions.

INTRODUCTION: Microorganisms are able to survive and induce persistent infection in periapical tissues. The aim of this study was to investigate the composition of the microflora of persistent apical periodontitis lesions. METHODS: Twenty apical lesion samples were obtained from 20 patients with chronic apical periodontitis by root end surgery and processed using aerobic or anaerobic culture techniques. All isolated strains were identified by 16S ribosomal DNA sequence analysis. RESULTS: Seventy-four strains were isolated, belonging to 31 bacterial species obtained from the 20 apical lesions that were isolated. The majority of the strains were facultative anaerobes (51.6%). Propionibacterium acnes, Staphylococcus epidermidis, Pseudomonas aeruginosa and Fusobacterium nucleatum were isolated from 16.2, 9.5, 6.8 and 5.4% of the samples, respectively. Fifteen samples harboured more than one species. The predominant association was P. acnes, S. epidermidis and F. nucleatum. CONCLUSION: The microbiota of persistent apical periodontitis lesions is composed by diverse types of microorganisms with biofilm-forming capacity, including P. acnes, S. epidermidis and F. nucleatum.

Colonization pattern of periodontal bacteria in Japanese children and their mothers.

BACKGROUND AND OBJECTIVE: The purpose of this study was to determine the time of infection by anaerobic gram-negative rods associated with periodontal disease, and to clarify their transmission from mother to child. MATERIAL AND METHODS: Seventy-eight Japanese children (including 10 siblings), aged from 3 to 9 years, and 68 mothers, were enrolled in this study. Colonization by 11 periodontal bacterial species was determined using polymerase chain reaction amplification of samples of subgingival plaque obtained from the children and their mothers. RESULTS: The detection rates of Porphyromonas gingivalis, Tannerella forsythensis and Treponema denticola increased in children after the age of 6 years. We found a high consistency in colonization by P. gingivalis, T. denticola, Prevotella intermedia and Prevotella nigrescens in 9 of the 10 siblings. The average number of bacterial species in plaque samples harboring Fusobacterium nucleatum and/or Fusobacterium periodonticum was significantly greater than in those without, in both children and mothers. Kappa statistical analysis revealed that the detection of Capnocytophaga gingivalis, Capnocytophaga ochracea, Campylobacter rectus and T. denticola in children was consistent with that in the mother. CONCLUSION: Periodontal bacterial colonization in Japanese children increased with age and was associated with F. nucleatum and/or periodonticum, and the bacterial flora in children was similar to that in their mothers.

Arg-gingipain A DNA vaccine prevents alveolar bone loss in mice.

One major pathogenic factor of Porphyromonas gingivalis is Arg-gingipain (Rgp), an arginine-specific cysteine proteinase. To clarify the effect of rgpA DNA vaccine, we immunized BALB/c mice via the abdomen with a Gene Gun or via the nasal cavity weekly for 6 weeks. After immunization, the mice were challenged orally with P. gingivalis. Immunization elicited IgG responses against P. gingivalis in both groups. Nasal immunization also induced sIgA against P. gingivalis, although Gene Gun immunization did not. Reduction of alveolar bone loss was observed in both groups at 42 days following initial infection. This effect was more pronounced in the intranasal immunization group than in the Gene Gun group. The results of this study suggest that immunization with rgpA DNA vaccine via the nasal cavity is an effective method for preventing alveolar bone loss incurred by infection with P. gingivalis.

Differentiation effects by the combination of spheroid formation and sodium butyrate treatment in human hepatoblastoma cell line (Hep G2): a possible cell source for hybrid artificial liver.

The aim of this study was to investigate the feasibility of human hepatoblastoma cell line (Hep G2), which differentiates by spheroid formation, and treatment with sodium butyrate (SB) as a cell source for hybrid artificial liver (HAL). Hep G2 spontaneously formed spheroids in polyurethane foam (PUF) within 3 days of culture and restored weak ammonia removal activity. Treatment with SB, which is a histone deacetylase inhibitor, further increased the ammonia removal activity of Hep G2 spheroids in a concentration-dependent manner. The activation of ornithine transcarbamylase--a urea cycle enzyme--was significantly related to the upregulation of ammonia removal by spheroid formation, but scarcely contributed to the further upregulation following SB treatment. In contrast with ammonia removal, treatment with SB reduced the albumin secretion of Hep G2 spheroids in a concentration-dependent manner. In the PUF-HAL module in a circulation culture, the ammonia removal rate and albumin secretion rate (per unit volume of the module) of Hep G2 spheroids treated with 5 mM SB were almost the same as those of primary porcine hepatocyte spheroids. These results suggest that simultaneous use of spheroid formation and SB treatment in Hep G2 is beneficial in enhancing the functions of human hepatocytes with potential applications in regenerative medicine and drug screening.

Synthesis of phospholipid polymers having a urethane bond in the side chain as coating material on segmented polyurethane and their platelet adhesion-resistant properties.

Surface modification of segmented polyurethanes (SPUs) was carried out using new blood compatible polymers having both phospholipid polar groups and urethane bonds in the side chains. The polymers were composed of 2-methacryloyloxyethyl phosphorylcholine (MPC), n-butyl methacrylate (BMA) and methacrylate with a urethane bond (MU). The MPC copolymers were soluble in ethanol. The SPU membranes were immersed in an ethanol solution of MPC copolymers and dried in vacuo for coating. The surface formed was completely covered with the MPC copolymer which was confirmed by X-ray photoelectron spectroscopic analysis. The polymer coatings were hardly detached in water, ethanol and 40% aqueous solution of ethanol compared with poly(MPC-co-BMA) which did not have the MU moieties. Therefore, the MU moieties had affinity for the SPU. The surface modification of the SPUs suppressed platelet adhesion effectively after contact with platelet-rich plasma for 180 min.

Preparation and performance of protein-adsorption-resistant asymmetric porous membrane composed of polysulfone/phospholipid polymer blend.

To obtain protein-adsorption-resistant membrane for hemodialysis, we prepared a polymer blend composed of polysulfone and 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer (PSf/MPC polymer). The content of the MPC polymer in the PSf was 7 and 15 wt%. The asymmetric porous membrane was obtained by the dry/wet membrane processing method. The surface characterization of the PSf/MPC polymer membrane by X-ray photoelectron spectroscopy revealed that the MPC polymer located at the surface. The mechanical strength of the PSf/MPC polymer membrane did not change compared with that of the PSf membrane. On the other hand, the permeability of solute below a molecular weight (Mw) of 2.0 x 10(4) through the PSf membrane increased with the addition of the MPC polymer, which is considered to be an effect of the hydrophilic character of the MPC polymer. The amount of protein adsorbed on the PSf membrane from plasma was reduced by the addition of the MPC polymer. The permeability of low-molecular-weight protein (Mw = 1.2 x 10(4)) did not change even after the PSf/MPC polymer membrane was contacted with plasma protein solution for 4 h, whereas it decreased dramatically in the case of the PSf membrane. Platelet adhesion was also effectively suppressed on the PSf/MPC polymer membrane. Based on these results, the MPC polymer could serve as a doubly functional polymeric additive, that is, to generate a protein-adsorption-resistant characteristic and to render the membrane hydrophilic.

Interaction between phospholipids and biocompatible polymers containing a phosphorylcholine moiety.

Random and block copolymers containing a phospholipid polar group in their side chain were synthesized by the copolymerization between 2-methacryloyloxyethyl phosphorylcholine and styrene. These copolymers showed amphiphilic character, especially poly(methacryloyloxyethyl phosphorylcholine-block-styrene) formed stable polymer micelles in water. The interaction between natural phospholipid, dipalmitoylphosphatidylcholine and methacryloyloxyethyl phosphorylcholine copolymers was investigated. The amount absorbed of dipalmitoylphosphatidylcholine from its liposomal solution on to the poly(methacryloyloxyethyl phosphorylcholine-co-styrene) surface increased with increase of methacryloyloxyethyl phosphorylcholine composition. Moreover, when poly(methacryloyloxyethyl phosphorylcholine-block-styrene) was added to dipalmitoylphosphatidylcholine solution, organization of dipalmitoylphosphatidylcholine molecules and stabilization of bilayer structure of dipalmitoylphosphatidylcholine liposome were found. This means that methacryloyloxyethyl phosphorylcholine moieties in the copolymer have a strong affinity to dipalmitoylphosphatidylcholine molecules. The blood compatibility of methacryloyloxyethyl phosphorylcholine copolymers was also investigated with particular attention to the aggregation ability of platelets after contacting methacryloyloxyethyl phosphorylcholine copolymers; this ability decreased when platelets were put in contact with polymers without a methacryloyloxyethyl phosphorylcholine moiety. On the other hand, aggregation ability remained at almost the same level to that of original platelets after contact with methacryloyloxyethyl phosphorylcholine copolymers. From these findings, we concluded that methacryloyloxyethyl phosphorylcholine copolymers show excellent blood compatibility due to adsorption of lipids from plasma and the formation of an organized adsorption layer of lipids on the surface of the methacryloyloxyethyl phosphorylcholine copolymers.

Modification of polysulfone with phospholipid polymer for improvement of the blood compatibility. Part 1. Surface characterization.

To improve the surface blood compatibility of polysulfone (PSf) membranes, we prepared novel polymeric additives which have suitable blood compatibility. They were polymers with a phosphorylcholine group, a 2-methacryloyloxyethyl phosphorylcholine (MPC) unit. The MPC polymer could be blended with polysulfone by a solvent evaporation method during membrane processing, and a transparent membrane could be obtained. The mechanical properties of the blend membrane were similar to that of the original PSf membrane. Surface analysis of the blend membrane by X-ray photoelectron spectroscopy and dynamic contact angle measurement revealed that the MPC unit in the polymeric additive was concentrated on the surface of the membrane. The blend membrane significantly reduced plasma protein adsorption compared with that of the PSf membrane.

Modification of polysulfone with phospholipid polymer for improvement of the blood compatibility. Part 2. Protein adsorption and platelet adhesion.

Protein adsorption and platelet adhesion from human plasma on polysulfone (PSf) membranes modified with 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer were studied. The modification was carried out by blending of the MPC polymer in the PSf. The amount of protein adsorbed on the PSf/MPC polymer blend membrane was significantly decreased with an increase in the composition of the blended MPC polymer. The distribution of the specific proteins adsorbed on the membrane surface was also determined by a gold-colloid immunoassay. Albumin, gamma-globulin and fibrinogen were observed on every membrane surface after contact with plasma. However, in the case of the blended membrane, the density of the adsorbed proteins decreased compared with that of original PSf membrane. That is, the MPC polymer blended in the membrane could function as a protein-adsorption-resistant additive. The number of platelets adhered on the PSf membrane was reduced, and change in the morphology of adherent platelets was also suppressed by the modification with the MPC polymer. Therefore, the PSf/MPC polymer blend membrane had improved blood compatibility compared with the PSf membrane.

Performance of adhesive bone cement containing hydroxyapatite particles.

A new acrylic bone cement which can adhere to both bone and prostheses was developed based on a methyl methacrylate (MMA) monomer containing 4-methacryloyloxyethyl trimellitate anhydride (4-META) as adhesion promoting agent. Moreover, hydroxyapatite (HA) particles were introduced into the 4-META cement as a bone compatible filler. The mechanical strengths of an acrylic bone cement without 4-META decreased drastically with an increase in the percentage of HA particles in the cement. However, the mechanical strengths of the HA-containing 4-META cement did not change in the same way as that of the 4-META cement without HA due to adhesion between the cement HA particles and matrix. The HA particles did not affect the adhesion of the 4-META cement to bone and metals. Implantation of the 4-META cement and the HA-containing 4-META cement in animals demonstrated that these cements did not disturb bone ingrowth and the new bone was able to contact the cement directly. The 4-META cements, with and without HA particles, could adhere to bone in vivo.

Chemical modification of silk fibroin with 2-methacryloyloxyethyl phosphorylcholine. II. Graft-polymerization onto fabric through 2-methacryloyloxyethyl isocyanate and interaction between fabric and platelets.

2-Methacryloyloxyethyl phosphorylcholine (MPC) was grafted onto silk fabric in a two-step heterogeneous system through the vinyl bonds of 2-methacryloyloxyethyl isocyanate (MOI) modified on the fabric. First, habutae silk fabric was modified with the MOI monomer in anhydrous dimethyl sulfoxide using di-n-butyltin (IV) dilaurate and hydroquinone at 35 degrees C. The saturated weight gain of modified MOI monomer on the fabric was 7.3 wt% versus the original silk. Second, graft polymerization with MPC onto the MOI modified silk was conducted using 2,2'-azo bis[2-(2-imidazolin-2-yl)propane dihydrochloride] (VA-044) as an azo polymerization initiator. The weight of the grafted MPC eventually gained was about 26.0 wt%. The MOI-modified and MPC-grafted silk fabrics were analyzed by Fourier transform infrared (FT-IR) spectroscopy. To confirm the improved biocompatibility of the silk fabric, platelet adhesion was preliminarily tested measuring lactate dehydrogenase. The number of platelets adhering to polyMPC-grafted silk fabric decreased by about one tenth compared to original and MOI-modified silk after 60 min of contact with human platelet-rich plasma (1.0 x 10(6) platelets cm(-2)).

Improvement of blood compatibility on cellulose dialysis membrane. I. Grafting of 2-methacryloyloxyethyl phosphorylcholine on to a cellulose membrane surface.

A methacrylate with a phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine (MPC), was grafted on cellulose membrane for haemodialysis in an aqueous medium using cerium ion (Ce4+) as an initiator. The effects of the concentrations of MPC and Ce4+, and degassing of feed solution on the grafting of MPC on the surface and the membrane properties such as permeability and mechanical strength were examined. The grafted MPC composition depended on the concentrations of both the monomer and initiator in the feed solution. When the grafted MPC distribution was controlled by the monomer concentration, the permeability of the membrane decreased with an increase in grafted MPC distribution. On the other hand, the permeability was not changed from the original membrane's value when the MPC distribution was regulated by Ce4+ concentration. The tensile strength of the membrane did not change during the grafting of MPC and this indicated that the grafting had taken place in the amorphous region of the cellulose. These results suggested that this method is a promising way to improve the blood compatibility of a cellulose membrane without having an adverse effect on the haemodialysis membrane.

Preparation of nanoparticles composed with bioinspired 2-methacryloyloxyethyl phosphorylcholine polymer.

The poly(L-lactic acid) nanoparticles immobilized with 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, which has excellent blood compatibility, were prepared by a solvent evaporation technique using the water-soluble amphiphilic MPC polymer as an emulsifier and a surface modifier. The diameter and zeta-potential of the obtained nanoparticles strongly depended on the concentration of the MPC polymer. When the nanoparticles were prepared in 1.0 mg/ml of an MPC polymer aqueous solution, the diameter was 221 nm which was determined by atomic force microscopy and dynamic light scattering measurements. The X-ray photoelectron spectroscopic analysis indicated that the phosphorylcholine groups of the MPC unit were located at the surface of the nanoparticles, that is, the MPC polymer was immobilized on the PLA particles and the surface zeta-potential was -2.5 mV. Various hydrophobic fluorescence probes could permeate through the MPC polymer layer and adsorb on the PLA surface. The amount of bovine serum albumin adsorbed on the nanoparticles was significantly smaller compared with that on the conventional polystyrene nanoparticles. It is suggested that the nanoparticles immobilized with the MPC polymer have the potential for use as both a novel drug carrier and diagnostic reagent which can come in contact with blood components.